1. Field of the Invention
The present invention relates to a shock-detonation transition type two-stage optical detonator.
2. Description of the Prior Art
A two-stage detonator is currently used to provide an optical detonator with low-power laser sources such as laser diodes for space applications: the first stage is used for thermal ignition of combustion by the laser and the second stage is dedicated to a blast-detonation transition.
A metal membrane at the interface between the two stages is cut by the combustion pressure in the first stage to form a plate which acts as a piston and compacts the porous explosive of the second stage and initiates combustion which, because of the confinement, initiates a blast-detonation transition process.
The disadvantages of this concept are associated with the use of the blast-detonation transition process. This necessitates:
the use of a low charge density (1.1 g/cm3) explosive, in fact one with a density close to the density of compacting to have a high porosity and also large particle size: this increases the sensitivity of the pyrotechnic component and is not favorable to good reproducibility of charging in its small components, and
a sufficient length of the second stage to reach the detonation transition point: in practice this significantly increases the quantity of explosive used.
The object of the present invention is to remedy the above disadvantages.
The invention therefore provides a shock-detonation transition type two-stage optical detonator wherein a first stage contains a pyrotechnic substance and an optical fiber one end of which is connected to a source of laser radiation and the other end of which is adjacent the pyrotechnic substance and is inserted into a connector and means between the end of the optical fiber and the pyrotechnic substance to transmit laser radiation towards the pyrotechnic substance and wherein a second stage contains a pyrotechnic substance aligned with the pyrotechnic substance of the first stage and separated therefrom by means for transmitting a shock wave generated by igniting the pyrotechnic substance of the first stage and the means separating the pyrotechnic substance of the first stage from that of the second stage comprise a metal plate one face of which is in contact with the pyrotechnic substance of the first stage and whose other face is adjacent a cavity which separates it from the pyrotechnic substance of the second stage and whose edge portion bears against the end of a confinement member confining the pyrotechnic substance of the second stage.
Because of the live combustion pressure generated on igniting combustion of the first stage pyrotechnic substance, the above metal plate is propelled at high speed onto the bare surface of the pyrotechnic substance of the second stage.
On impact, the plate triggers a shock-detonation transition in the pyrotechnic substance.
That shock-detonation transition is encouraged by focusing the shock wave.
The shock-detonation transition enables the manufacture of a shorter detonator which contains less pyrotechnic substance, which is less sensitive and more reproducible and which has a shorter response time than the solution referred to at the beginning of this description.
The diameter of the cavity is preferably greater than that of the second stage pyrotechnic substance and an end face of the second stage pyrotechnic substance adjacent the cavity is preferably coincident with the face constituting the end wall of the cavity.
Thus on impact the plate collides simultaneously with the pyrotechnic substance and with the end face of the cavity. This focuses the shock wave onto the pyrotechnic substance.
Other features and advantages of the invention will become more apparent in the course of the following description, which is given with reference to the accompanying drawing, which is provided by way of non-limiting example only.